What does needing to hit my flashlight to switch it on indicate?

I'm the new guy, love this forum, being frugal is awesome and I love bright lights!

Thanks for having me, please forgive me if this is the wrong part of the forum to post this or its been asked to death already.

I've noticed on all my flashlights almost without fail they start to need a solid smack/blow(normally I hit the flashlight into the palm of my hand or leg etc) to switch on, then typically once they are switched on they run fine(or not and intermittently flicker on/off till it drives me nuts and I smack it again till it comes right again).

What does this behaviour indicate?

Seems to me its a loose contact somewhere probably in the tail switch but I'm not 100% sure, whatever it is its damn irritating, drives me crazy!!

Welcome to BLF!!

Well, all depends... Are they LED lights? I know with the old regular bulb cheaper lights I used to own, I found that was needed often. The LED lights can be more reliable, but depends on a few things. If you are in a high humidity or salt water environment, the contact surfaces can take a beating, so you are getting intermittent connections. I've seen in some lights,, the springs actually de-solder themselves, and can usually work, but can be intermittent. Depends a lot on environmental conditions, metal to metal contacts getting oxidized (not treated with any electrically conductive grease), cells not being replaced for long times, solder connections failing, etc.

We need to know the brand & model of flashlights that are having these problems.

Loose retaining ring on the switch. If it’s a single cell alkaline then it doesn’t take much in the way of dirt or corrosion to affect a cheap light. Loose threading on the pill or poor driver ground can also cause this. Even 18650 lights can do this as well.

It indicates that you need a new flashlight…. :smiley:


Check the retaining ring on the switch. Since this is happening with all your lights, it could be because of the way you turn them on (hitting them really hard, etc.). Might cause the retaining ring to loosen over time and result in odd behavior.

Nah....just a few more...to start that is..

It happens on AA, 2xAA, 1 x 18650, all budget chinese LED lights, they aren't worked hard or used in rough environmental conditions.

The switch retaining ring seems like a good place to start. How do I check the threading on the pill(thats the board that carries the LED emitter?

This issue isn't as a result of me hitting the flashlights as I only start hitting them to switch on after the issue crops up.

Welcome to BLF!
Maybe post some pics?

If there is battery slop and the battery rattles in the tube it can cause some intermittent problems…

one vendor wrote …Most issues are electrical connection issues .length of spring or length of battery // i have some lights that demand a button top or a solder blob on a laptop pull to run at all .

tailcap issues are generally solved by a quick dissassembly alcohol clean and reassemble .

if you have battery rattle you can take a drinking straw and slit it up the side cut it a bit shorter than the cell and wrap it around the battery …slick enough to let the cell slip out when you recharge your batteries.

2xAA lights always have a lot of battery rattle and I think the straw helps the light feel and act much better .Just cut it twice as long …
Try it you’ll like it

On my older lights, those happens due to the switch assembly itself. They tend to get sticky internally. Normally I open the switch, clean, wd40 some, pull the spring a bit to strengthen and reassemble. Works great normally, unless some bit jumped and escaped. :smiley:

Switches are cheap btw if you dont want the trouble.

If you’re getting these problem on all your lights, and they all happen to use mechanical switches, then you might want to consider buying some lights that use electronic switches. There’s a lot of benefits to electronic switches, including they are more reliable. The only significant downsides is they usually don’t support “tactical” applications (such as a forward mechanical switch allows), and if they do fail they can’t usually be repaired by yourself. I’ve never had an electronic switch fail on me, though.

Clean the ends of the cells, in fact, clean everything. If the switch and pill is removable then do so and clean everything you can get at except the reflector, avoid touching its inside surface as all you will do is scratch it or contaminate it. The pill grounds the driver to the host and dirty threads cause issues. Weak springs are another culprit, they can compress over time and lose the force with which to maintain contact. Stretching them can be a temporary fix and indicate the need for stronger springs.

Thanks for all the solid advice, what is the correct tool for unthreading the round lockring with 2 holes in them that holds the tail-switch/pill?

This thing:

Anything that will work, but most use needle nose pliers, or tweezers.

Some lights use left-hand threads on the switch retaining ring.

So you have to use a left handed screw driver obviously? :wink: